1. Field of the Invention
The present invention relates to a computer program product, system, and method for performing a remote point-in-time copy to a source and target storages in further mirror copy relationships.
2. Description of the Related Art
In a storage environment, a storage controller may create point-in-time (“PiT”) copies of a production volume using point-in-time copy techniques, such as the IBM FlashCopy® (FlashCopy is a registered trademark of IBM), snapshot, etc. A point-in-time copy replicates data in a manner that appears instantaneous and allows a host to continue accessing the source and target volumes while actual data transfers to the target volume are deferred to a later time. The point-in-time copy appears instantaneous because complete is returned to the copy operation in response to generating the relationship data structures without copying the data from the source to the target volumes. Point-in-time copy techniques typically defer the transfer of the data in the source volume at the time the point-in-time copy relationship was established to the copy target volume until a write operation is requested to that data block on the source volume. Data transfers may also proceed as a background copy process with minimal impact on system performance. The point-in-time copy relationships that are immediately established in response to the point-in-time copy command include a bitmap or other data structure indicating the location of blocks in the volume at either the source volume or the target volume. The point-in-time copy comprises the combination of the data in the source volume and the data to be overwritten by the updates transferred to the target volume.
In a mirror copy relationship, a primary storage comprises the storage or volumes from which data is physically copied to a secondary storage or volume. To address a situation where a mirror primary volume on a local site becomes the target of a PiT copy or FlashCopy operation from a source volume on the local site, which source volume may also be a primary volume in a mirror copy, IBM developed the Remote Pair FlashCopy operation so that when data is FlashCopied, i.e., PiT copied, from a source volume to a target volume on a local site when the source and target volumes are also primary volumes in mirror copy relationships to secondary volumes at a remote site, an equivalent FlashCopy operation is performed on the remote site to FlashCopy the remote secondary volumes in the mirror relationship so that the mirror copy to the secondary volumes can be accomplished instantly with a PiT copy.
This Remote Pair FlashCopy operation ensures that the mirror copy relationship is not interrupted due to the primary storage in the mirror relationship becoming the target of a FlashCopy relationship. With Remote Pair FlashCopy, when the FlashCopy source and target devices are both mirror primary devices in full duplex state, the FlashCopy is performed locally between the source and target, i.e., the primary volumes in the mirror relationship, and then the FlashCopy is sent inband to the FlashCopy server having the secondary volumes of the mirror and performed remotely between the two secondary volumes.
By ensuring that the mirror relationships are not interrupted by the FlashCopy operation, the mirror storages remain available for a failover operation from the mirror secondary storage to the mirror primary storage, such as the IBM HyperSwap®, which provides continuous availability for disk failures by maintaining synchronous copies of all primary disk volumes on one or more primary storage systems to one or more target (or secondary) storage systems. (HyperSwap is a registered trademark of IBM in countries throughout the world).